The field of the invention relates generally to electronic trip units (ETUs) and more particularly to power management within an ETU.
An electronic trip unit is a device that protects a circuit and equipment connected to the circuit. In industrial settings, for example, an ETU serves to prevent damage to equipment and machines that, in many cases, represent a significant investment by a business and on whose operation the business relies. An ETU carries out this function by monitoring electrical current through a line and, if the current exceeds a certain threshold, will open a switch in the line, thereby preventing further current from reaching devices that would be damaged by the excessive current. The switch may be opened and closed by, for example, an electromechanical actuator.
Given the role that an ETU plays in protecting the equipment connected to it, it is correspondingly important to ensure that the ETU is in proper working order, through diagnostics and maintenance. A special-purpose testing kit, external to an ETU, is typically needed to determine the status of the ETU. The testing kit is designed and configured to provide power to the ETU and determine whether any malfunctions have occurred. For example, the testing kit provides an electrical command, along with sufficient power, for the ETU to actuate the circuit breaker. Without the special-purpose testing kit, a technician is unable to perform the above diagnostics.
Some data-communication connections, such as Universal Serial Bus (USB) connections, provide power from a host device to one or more devices connected to the host. Most general-purpose computer devices, such as laptops and personal computers, are configured to act as USB hosts. Moreover, battery packs, wall outlet power supplies, and other power-supplying devices with USB host power capabilities are common. However, tripping an industrial circuit breaker requires more power than a USB connection is able to provide directly. Accordingly, USB host devices are unable to act as replacements for the special-purpose testing kits described above.